Preheat the Oven: Preheat your oven to 325°F (160°C). Line a 9×9-inch baking pan with parchment paper, allowing it to overhang on the sides for easy removal.

Prepare the Crust: In a medium bowl, combine graham cracker crumbs, sugar, and melted butter. Mix until the crumbs are well coated. Press the mixture firmly into the bottom of the prepared pan to form an even layer. Bake the crust for 10 minutes, then remove from the oven and let it cool.

Make the Raspberry Swirl: In a small saucepan over medium heat, combine raspberries, sugar, and lemon juice. Cook until the raspberries break down and the mixture thickens slightly, about 5-7 minutes. Strain the mixture through a fine-mesh sieve to remove seeds, if desired. Set aside to cool.

Prepare the Cheesecake Layer: In a large bowl, beat cream cheese and sugar with an electric mixer until smooth and creamy. Add eggs, one at a time, beating well after each addition. Mix in vanilla extract and flour until smooth. Stir in the sour cream until fully incorporated.

Assemble the Bars: Pour the cheesecake mixture over the cooled crust. Smooth the top with a spatula. Drop spoonfuls of raspberry sauce over the top of the cheesecake layer. Use a toothpick or knife to swirl the raspberry sauce into the cheesecake.

Bake the Cheesecake Bars: Bake for 35-40 minutes, or until the center is set and the edges are lightly golden. Remove from the oven and allow to cool to room temperature, then refrigerate for at least 3 hours or until fully chilled.

Serve: Once chilled, lift the bars out of the pan using the parchment paper. Cut into squares before serving.